Reading the dust patterns on your saddle pad is the equestrian version of reading tea leaves. You study the marks that are left after riding and they help you evaluate the pressure points under your saddle and if it’s a good fit for your horse. Of course, it can also tell you that your horse is dirty!
In general, wherever you see dirt, there is contact. Where there’s no dirt? No contact. Analyzing the dirt patterns can help you see if you are crooked in the saddle (more dirt on one side than the other), whether the saddle bridges (no dirt where you would expect to see contact)
According to master saddler Jochen Schleese:
The dirt should accumulate in the areas of the saddle pad that experience the most movement: at the front of the saddle (where the shoulder moves up and back) and at the back (where horse’s back swings). No dirt should show in the areas where the saddle doesn’t come in contact with the horse’s back, such as the gullet or at the transition between sweat flap and panel.
Just remember to start with a clean, white pad and a clean horse. If your horse isn’t pretty clean, excessive dirty on parts of its back can skew the results. Also, if your pad slips at all during your ride, it will impact the patterns.
Finally, your horse gets the final say in fit. I had a saddle a few years ago that created dirt patterns that, to me, indicated saddle fit problems. My horse apparently hadn’t read the manual because he loved that saddle. So sometimes the tea leaves don’t tell the whole story.